4. Structure Of Atoms
Electron was discovered by J.J. Thomson. Cathode rays consist of small, negatively charged particles called electrons. The electron is a negatively charged particle found in the atoms of all the elements. The electrons are located outside the nucleus in an atom. An electron is usually represented by the symbol e–
Characteristics of an electron
Mass of an electron :
The mass of an electron is about of the mass of hydrogen atom. Since the mass of a hydrogen atom is 1 u. The absolute mass of an electron is, however, 9 × 10–28 gram.
Charge of an electron :
The absolute charge on an electron is 1.6 × 10–19 coulomb of negative charge. The relative charge of an electron is, – 1.